Method and apparatus for launching aircraft



April 8, 1947. R W N 2,418,702

METHOD AND APPARATUS FOR LAUNCHING AIRCRAFT Filed March 9, 1943 8 Sheets-Sheet l pr 1947. R. c. DU PONT METHOD AND APPARATUS FOR LAUNCHING AIRCRAFT Filed March 9, 1943 8 Sheets-Sheet 2 P 8, '1 947. R. c. DU PONT METHOD AND APPARATUS FOR LAUNCHING AIRCRAFT Filed March 9, 1945 8 Sheets-Sheet 3 April 8, 1947. R. c. DU PONT 2,418,702

METHOD AND APPARATUS FOR LAUNCHING AIRCRAFT Filed March 9, 1943 8 Sheets-Sheet 4 April 8, 1947. R. c. DU o -r 2,418,702

METHOD AND APPARATUS FOR LAUNCHING AIRCRAFT Filed March 9, 1945 8 Sheets-Sheet 5 April 8, 1947. R. c. DU PONT 2,418,702

METHOD AND APPARATUS FOR LAUNCHING AIRCRAFT I Filed March 9, 1945 8 Sheets-Sheet 6 April 8, 1947. R. c. DU PONT 2,418,702

METHOD AND APPARATUS FOR LAUNCHING AIRCRAFT Filed March 9, 1943 8 Sheets-Sheet 7 luv 8111611 Reclai ama April 8, 1947.

R. c. DU PONT METHOD AND APPARATUS FOR LAUNCHING AIRCRAFT Filed March 9, 1943 8 Sheets-Sheet 8 Engenfm R f Patented Apr. 8, 1947 METHOD AND APPARATUS FOR LAUNCHING AIRCRAFT Richard C. du Pont, Granogue, Del., assignor to All American Aviation, Inc., Wilmington, Del., a corporation of Delaware Application March 9, 1943, Serial No. 478,517

26 Claims. 1

My invention relates to mechanisms and methods for launching a glider or a powered aircraft by means of another aircraft.

It is the purpose of my invention to provide a method of launching either gliders or powered aircraft which will be efficient, safe and foolproof particularly when used with large aircraft. It is particularly useful in assisting in launching powered aircraft and gliders which are in motion when launching contact is made.

A further object of my invention is to provide a method and apparatus for launching either a glider or a powered aircraft from water.

A further object of my invention is to provide a method and apparatus whereby powered aircraft will be enabled to take-off from a location which because of its small size r because of the overloaded condition of the aircraft, would not permit normal unassisted take-off.

A further object is to provide a method and apparatus whereby the pay load or the cruising range of aircraft may be greatly increased.

A further object is to provide means whereby the pickup line or loop may be supported in a position for engagement entirely independently of the type of surrounding terrain.

A further object is to provide safety devices for the technique of assisting the take-01f of aircraft to render said technique safe and practical.

A further purpose is to use the special energy absorbing and elongation qualities characteristic of Nylon, Laminite, Saran, Vee Plastic and other synthetic fibers in the tow line to relieve the shock of impact in the launching operation.

Further purposes will appear in the specifications and in the claims.

My invention relates not only to the methods involved but to mechanism by which these methods may be carried out.

In the drawings I have preferred to illustrate main forms and also suihcient detail to show various ways in which the methods may be carried out.

Figures 1, 2 and 3 are perspective views showing towing aircraft (tugs) and aircraft which are being launched, in various positions, illustrating the launching operation.

Figure 3 is a fragmentary View similar to a part of Figure 3 but showing an assisted aircraft which carries supplemental tow line drum, brake and rewind mechanism for payout, and rewindmg.

Figures 4 and 5 are fragmentary, perspective, largely diagrammatic views of successive positions during. a pick-up.

Figures 6, 12, 13, 14 and 15 are fragmentary, perspective views exhibiting various forms of loop-supporting post-s mounted upon rudder assemblies.

Figure '7 is a fragmentary side elevation of a portion of the structure of Figure 6.

Figure 8 is a side elevation of a pulley secured to the rudder assembly in Figure 6.

Figure 9 is a side elevation of the pulley and tip of loop supporting pole in Figure 6.

Figures 10 and 11 are a side elevation and a top plan view, respectively, of part of the structure seen in Figure 9.

Figure 16 is a fragmentary side elevation of posts such as might be used inFigure 15.

Figures 1'7, 18 and 25 are top plans of fittings of the general type shown in Figures 14, 15, 16 and 24.

Figure 19 is a side elevation of a clip for positioning a loop when releasable poles are used as in Figure 3.

Figure 20 is a perspective view showing a wingmounted post for supporting a take-01f loop, embodying one form of the invention.

Figure 21 is a perspective of a clip and plate by which the loop or leader attached to the towed aircraft may be held removably to a wing or fuselage to permit tension withdrawal.

Figure 22 is a fragmentary, perspective view showing posts which have been removed from the rudder assembly of such a structure as Figure 14 or from a wing mounting.

Figure 23 is a fragmentary elevation of the upper part of one of the posts and post fittings.

Figure 24 is a fragmentary side elevation of a post such as would be used in Figure 14.

Figure 26 is a perspective view of a spring clip for holding the pole in place in Figure 14.

Figure 27 is a perspective view of the tip of a pick-up arm and a mechanism for positioning a pck-up hook.

Figure 28 is a cross section of the arm of Figure 2'? on line 282B.

Figure 29 is a cross section through hook positioning mechanism on lines 29-29.

Figure 30 is a perspective view of a pick-up hook.

Figure 31 is a cross section of the releasing mechanism shown in Figure 3.5 in the closed or towing position and with a different operating mechanism.

Figure 32 shows the releasing mechanism of Figure 31 in the open or released position.

Figure 33 is an end elevation of the structure seen in Figures 31 and 32.

Figure 34 is a fragmentary diagrammatic view, partly sectioned, showing control mechanism for disconnecting the tow loop for operating the release mechanism of Figures 31 and 32.

Fi ure 34 is a diagrammatic view showing a modified form of operation of Figure 34.

Figure 35 is a fragmentary figure, partly .in elevation and partly in section, showing radio control for tow line releasing mechanism,

Figure 36 is a cross section showing a sheave wheel seen in Figure 35.

Figure 37 is a fragmentary perspective view showing the installation of pick-up mechanism in the towing aircraft or tug.

Figure 38 is a perspective view, partly broken away. showing drum and brake mechanism used, slightly modified.

Figures 39 and 40 are fragmentary perspective views of parts of the drum and brake mechanism seen in Figure 38.

Figure 41 is a fra mentary enlarged longitudinal section of a-modified form shown inthe structure seen in Figure 39.

Figure 42 is a section of Figure 41 taken upon line 4242 of Figure 41. v

In the drawings similar numerals indicate like parts.

Figure 1 shows an embodiment of my invention as applied to a multi-engine flying boat indicated in general at M, which is being launched and which may assist in it launching by a part of its engine power or by all of its engine power. In either case the use of the tug or towing aircraft 45 permits a take-off ina shorter distance than could otherwise be accomplished and in the case of an overload an aircraft can be launched which couldnot otherwise take off under its own power. The flying boat is provided with a. loop 46 which is caught by a hook 4i directed by an arm 48 depending from the tug or towing aircraft.

In use, when the loop 46 has been picked up; the hook l! disconnects from the arm 48 as hereinafter more ful y expla ned and is supported by a drum-wound towing cable 49.

3 There is no novelty in the motors wings, steering mechanism and other aircraft features either of the air tug or of the aircraft launched or towed.

While a loop is illustrated as being the preferred formof tow line connection, it is to be noted that a single line has been used successfully i" in other types of air pick-up operations and my invention contemplates the use of either a loop or a section of line for this purpose. The term loop will, therefore, be understood to contem plate either an actual loop or a line stretched transversely to the path of the tug and connected with the aircraft being launched.

It is important that the loop or line to be caught by the hook depending from the air tug shall be supported from the aircraft to be launched though it is recognized that the way in which theloop or line is supported may be varied greatly. Because the aircraft to be towed will ordinarily be little suited to furnish the support to the loop directly, it will ordinarily be necessary to supply at least one pole for loop support and it will ordinarily be advantageous to provide. two poles for its support. Moreover, because a loop is. more convenient and eiiective thisv form has been chosen for illustration. in order to present the best embodiment of the invention known. to applicant.

Whatever the character of support, whether attached to the plane or detachable therefrom, there is a distinct advantage in mounting the support upon the upper part of the structure of the aircraft towed; this is true whether the aircraft be sea-borne or land-borne before launch- With sea-borne aircraft, there is inherent difficulty in supporting a loop for positive engagement by the tug aircraft unless loop supports are carried by the aircraft to b launched. This is true even when the aircraft to be launched does not assist in the launching, and it is particularly true when there is to be assistance in the launching by the use of part or all of the power of the aircraft launched or by a sea-borne tug before actual pick-up contact is made.

Mounting of loop supports upon the aircraft applies not only to an assisted take-01f where the seaplane or land plane assisted is in motion at the time of contact but to a pick-up where the seaplane or land plane is stationary at the time of contact and whether the aircraft launched be a powered aircraft or a glider.

Mounting the loop upon the aircraft launched would apply also whether the aircraft launched be given motion by reason of its own power or independently as by use of a tractor or tug boat. In either of these cases land mounted poles would be unsuitable.

Considering next a variety of general classes of poles which may be used and which are illustrated, I will describe first the poles which are carried permanently by the aircraft to be launched, and then I will describe poles which are mounted initially upon the aircraft to be launched but which either are cast on from it altogether or are removed from it by the loop.

In. Figure l. the loop is stretched between poles 50 permanently mounted upon vertical fins 5 I.

In the form shown in Figures 6, '7, 8, 9, 10 and 11 the tips cf'the poles 5i! carry sheathed pulleys 52 around which are threaded an endless line 53. To this line is attached a clamp 54 having a flexibly mounted spring clip 55 near its lower edge. The. upper. edge of. the clamp 54 is flared to prevent it from passing over the pulley 52.

The lower part of. the endless line 53 passes around a second sheathed pulley 55 attached to a plate 51, seen in Figure 8. It is located at an accessible portion of the lower inside surface of the vertical fin 5! with the axis of the second pulley at angle with respect to the axis of the first pulley. An operator can raise and lower the clip 55 while he is standing upon the tail surface 58, thus permitting him to insert the loop $6 or separated parts of a line within spaced clips 55 reliably and conveniently.

Figures 6, '7, 8, 9, l0 and 11 illustrate the construction of one of the poles 55 shown in Figure 1. Since these poles are permanently attached to the vertical fins, they are made in streamlined shape as shown in Figure 11 in order to reduce the air drag.

Portions of 10051 35 at. opposite fins are removably held in the clips 55, between which clips the loop is. stretched to present a reasonably taut transverse stretch 59 for engagement by the pick-up hook 47. I

On each side of the transverse stretchv the loop terminates in a leader 6B which is threaded detachably through open brackets 51 to .a point near the nose of the flying boat at which point it, or a fitting attached to it, is secured to the boat for towing purposes. The brackets prevent fouling in this form and in other forms.

The attachment can be by a noose 62 in the end of the leader itself inFigure l, for example,

or the leader can be connected to a ring or other fitting 63 as seen in illustrations of disconnecting devices later illustrated.

The noose, ring or other fitting, hereafter called ring is inserted in release mechanism broadly indicated at 64, Figure 31, and which is secured to or upon the structure of the flying boat. The tension in the clips is sufiicient to hold the upper transverse stretch of the loop substantially taut and at the same time to permit the loop to release readily from the clips as soon as it has been engaged by the hook. When released from the clips the loop assumes successive positions such as are shown in Figures 4 and 5 and the hook 41 slides from the lower end of arm 48 so as to be supported wholly from towing cable 49, all as more fully later described.

In installations where it may become necessary to prevent endless line 53 from turning in pulleys 52 and 56 after clips 55 have been raised to the tips of the poles, a cleat 65 or other common friction device may be installed to prevent accidental movement of line 53.

Because the poles 50 are mounted each upon the upper end of a fin 5| they can be much shorter than would otherwise be necessary and permanent mounting of these poles upon the aircraft to be launched becomes much less objectionable than the mounting of full length poles.

The present invention offers alternatives to the fixed poles of Figures 6-11, (a) telescopic poles mounted upon the vertical fins; (b) poles wherever mounted which, after use, are cast off wholly from the aircraft; (0) poles which are carried away from the aircraft but remain attached to the loop, Each of these is given for illustrative purposes as an example, a species representing a type.

The variety of means for supporting the loop or tow line illustrates the fact that quite different types of poles and varying operative constructions can be used in practice of the present invention.

A second form of pole, different from the permanently afiixed poles of Figure 1 and of Figures 611, is shown in Figures 12 and 13. It comprises poles permanently attached to the vertical fins but dropping below their upper ends when not in use, in order to avoid the undesirable air drag attendant upon having poles extending from a portion of the aircraft during fiight.

The telescopic poles 50' may be lifted by hand and retained by lateral pull upon them from the loop (line). On account of their size and weight, however, they will ordinarily be operated by fluid pressure in pipe 66. After use, they can be dropped by their own weight when the fiuid pressure has been relieved. The loop is removably secured in clips 55 at the upper ends of the poles, of the same general character as those shown in Figure 9.

Where it is the intention to hold the poles in raised position by the lateral and forward pull of the loop, the loop can be held stretched to any extent desired which will not pull it out of the clips and the poles may be held erect by using a loop holder 51 such as appears in Figure 19. The use of such a holder is shown in Figure 3, in which the open end of the holder engaged the end of the loop adjacent the leader prior to contact by the tug, said open end of the holder eing directed toward the front of the aircraft so that as the pick-up hook d1 carried initially by arm lii engages the stretch of the loop and pulls it loose from the clips 55 (Figure 15), carrying the loop forward, this act will loosen the loop from the holder and the continued pull of the pick-up hook 4! upon the loop will pull the loop forwardly out of engagement with the holder.

The steps in this procedure are generally indicated by Figures 3, 4 and 5; however, it will be understood that Figures 4 and 5 illustrate the fixed pole installation of Figure 1 which does not require a holder 61 as would the disposable poles of Figure 15. Figure 3 shows the plane which has been equipped with these disposable poles.

At or before the time the loop is pulled to the position seen in Figure 3 the hook will be disengaged from the arm 48 and will be carried wholly upon towing cable 49 as seen in Figures 3 and 5. V

In variou figures rungs 68 are shown upon the vertical fins, to serve as steps for access to the upper parts of the vertical fins and the tops of the poles, so that an operator can climb up and insert the loop in the clips at the tips of the poles. In the telescopic form this will ordinarily be done before the poles have been raised to their full height either manually or hydraulically but the rungs are useful in any of the forms showing vertical fins.

Figure 2 illustrates my invention applied to a land glider M which, of course, has no engine and which mounts poles 50 near the wing tips of the glider by means of sockets 59 shown in relatively enlarged view in Figure 20. The clips 55 at the tips of the poles 50 are or may be identical with corresponding clips seen in Figure 9.

The poles 50 are wholly removable and rest in the sockets 69 and against shields ill in such a way that they may be held in place against premature loss by the tension of the loop. This may require the use of additional lateral spring tension on the loop in clips 6| nearest to the poles.

The shields or extensions iii are preferably located in the direction of the first bracket 6| from the socket recess. The shields retain the poles in an upright position so long as the loop exerts tension upon the poles 50 but at the instant the loop pulls free from the clips and motion is imparted to the glider, the poles 56 will fall out of the sockets, due to a combination of air drag and the forward velocity of the ship. The poles are thus completely discarded and any wind drag or stress during flight is eliminated. The stretch 59 of the loop or line is maintained taut by the friction of the clips 55.

It will be noted that the stretch here and at other points in my disclosure need not be horizontal provided it be accessible for the pick-up hook and does not slope sufiiciently in any direction to interfere with reliable pick-up by the hook.

In whatever form, it is desirable that the connection from the loop or line along the surface of the aircraft launched to the point of attachment upon the front of the powered plane or glider shall be held by tension-releasing clips to prevent fouling.

The main tow connection of the loop or line 18 with the towed aircraft is releasable at its point of attachment to the towed aircraft. Both hand and automatic releases for normal and emergency operation will be described hereinafter, In Figures 15, 16, 17 and 18, disposable poles 5B are shown which are suitable for use upon a powered body such as that in Figure 1. They may be attached to vertical fins as seen in Figure 15 and carry spring clips 55 within which the loop stretch 59 or other line may be supported so as to be tension released.

The detail of this form is shown best in Figures 16 and 17. Sockets ll similar to the sockets in Figure 20 receive the bases 12 of the poles 50 The supporting skirts 73 are similar to the shields of Figure 20. The skirts prevent the poles from falling or being removed in the direction of the skirt. The skirts face substantially forwardly. Above the sockets additional straps i4 encircle the poles about 180 carried by convenient spars l5 (Figure 1'7). Only one of each of the pair of parts is shown.

The straps also support the poles laterally, and in order to prevent the poles from falling backwards when the loop is attached to them, loop holder El is mounted on the outer surface ofthe aircraft inv some such position as in Figure 3. Sufiicient tension is thus exerted to prevent the poles from falling out.

The loop performs a double function here muc as itdoes in Figures 12 and 13 in that it not only affords a stretch to be picked up by the hook from the air tug but the tension of the loop holds the pole in position as in Figures 15, 16 and 18.

In Figures 14, 22, 23, 24, 25 and 26 still another type of pole and pole connection is shown for detachably supporting loop stretching poles from aircraft to be launched.

In Figure 14 the base Hi of the pole 56 rests in sockets 11 attached to a Vertical fin presenting the same general appearance as in other figures herein but with the dilference that the pole in this case, though removable, is carried with the loop.

The socket I1 is tiltable about a pin 18 so as to-ofier easier release for each pole from its socket than otherwise would be the case. The pin passes through a spacing bushing 19 intended to give a bearing surface and permit free release of the pole. It enters the spar 80. Brackets 8| upon plates 82 are mounted slightlyabove the sockets and support the poles While in place. They have openings which are disposed toward the center or" the aircraft in order that the pole may be released readily after contact. The loop is threaded through rings 83 at the pole tips (see Figure 23). The rings 83 thus carry the poles with the loop and securely support the poles from the loop.

When the hook engages 1311610013 46 the poles are pulled fromthe supporting brackets and remainwi-th the loop during the further launching and towing operation in some such position as shown in Figure 22.

There is a distinct advantage in this method when launching from the water or from places where the poles otherwise are not readily recoverable.

The difierent poles illustrated show that the important thing is to support the pick-up line or loop from the aircraft launched or towed, so that the stretch to be picked up is independent of outside surrounding ground or water conditions' and will travel with the aircraft to be launched. It may be possible to support the line or loop directly from the aircraft structure at one or two points. The same considerations make it possible that only one pole may be needed and that where a pair of poles is used they need not be of thesame type.

. Figures 1. and 2 both illustrate a towing aircraft or. tug about to launch a second aircraft, the second aircraft in Figure 1 being a powered aircraft which is being launched from the water and Figure 2' showing a glider without power being launched fromthe ground. Though it is the intention ordinarily to use the motors of a powered aircraft being launched to give the assistance in the launching this cannot be done in the case of Figure 2; and the assistance for the take-ofi can be provided by a land borne tractor, automobile or other craft for land launchings and in Figure 1 by using a tug or other powered boat in the case of launchings from the water.

After the aircraft has been launched it is towed as illustrated for one tug and tow in Figure 3. The towing cable from the air tug con nected with cable-carrying winch drum 84' carried in or on the air tug and is capable of being payed out under increasing friction and reeled in as later explained. In this illustration of Figure 3 the poles have been cast off wholly from the powered aircraft being towed and the connection from it to the leader may be by a noose 62 if desired or by some fitting such as the ring of Figures 31-33,

The parts of the towing connection between a towing aircraft or tug and a towed aircraft or tow are, or permissibly may be, the towing line, which is a drum-wound rope or cable, preferably a steel cable, whose drum, carried by an air tug, has a relatively high inertia, a pick-up. hook carried by the towing line, a pick-up loop or line, engaged by the hook, and a leader attached to the loop and to the tow. A leader is not always essential since the loop itself may be attached to the tow as shown in Figure 2.

In case of a large and heavy tow, permissibly the leader will be wound on a drum carried in the tow (Figure 3 and from which it may pay out.

When used, the drum for the section. of line payed out from the towed craft is ordinarily smaller than the drum carried by the tug and of relatively lower inertia than the inertia of the drum on the tug.

It will thus be apparent that as soon as the loop leader and cable have been pulled taut each one in effect becomes a tow line which is a part of the entire composite tow line or towing connection.

The tow line or towing connection consisting of leader, loop and line carried by the tug may entirely or partly, as desired, be composed of a synthetic or plastic material having inherent shock absorbing qualities. These qualities are found in Nylon, Laminite, Vee Plastic and other fibers as later further explained.

The arm 48, seen best in Figure 37, is attached to the tug by means of a yoke braced at its upper end to provide pivoted spaced bearing supports 85 which rock in the structure of the air tug. To the upper end of the yoke, a handle is attached.

The arm 43 can be raised and lowered by the handle. In pick-up use the arm 58, normally in its lowermost position, sloping rearwardly' and downwardly, is held down by the handle. It is not safe to have the arm in. this position .at all times. Just before or just after the pick-up of an aircraft the air tug may fly quite low. Sometimes also the tug attempts to land while the arm is down. A depending pick-up arm may then be injured by striking an obstruction. For this reason, in Figure 3'7 the handle used to swing the arm is held down yieldingly by a spring clasp 81 having spring side plates and flared upper edges 88..

When the handle is presseddown-to lowermost position it will spread the upper edges and enter the clasp. The tension in the side plates holds the handle down against air pressure and against the force of contact with the pick-up loop but greater pressures will cause the handle to spread the side plates and the arm will lift to upper protected position.

The cable 49 passes to and from the drum 35 through a strap block 89 carrying a guide pulley 9!], all mounted upon a retractabl triangular frame structure 9!. This frame is adapted to be thrown in counterclockwise direction, swinging through about 90 of angular movement, not shown, to an inactive position.

A spring guide member 92 blocks the space about the pulley from passage of the hook at in the position shown but slides upon bracket rods 93 to a position seen in dotted lines in Figure 37 to permit the hook to pass when desired.

In operation as so far described the aircraft to be launched and of which there is to be assisted take-01f, is operated by its own power or if it be a glider it is towed by a land borne craft or sea tug, so as to travel across the ground or water by one means or the other to overcome the additional inertia which it would have if stationary and thus to assist as much as possible with the towing aircrafts effort to get it into the air and to tow it to a point where the towing cable can be released.

While the aircraft to be launched is in motion the air tug in flight and with its towing arm 48 depending in position for use. picks up the stretch 59 of the line or loop 48, pulling the line or loop free-from the poles or carrying the poles along with the loop and freeing the loop or leader from its temporary attachments along the surface of the towed aircraft. The position of the loop therefore passes from that seen in Figure 1 or Figure 2 through the positions shown diagrammatically in Figures 4 and 5 to that shown in Figure 3.

As soon as any appreciable tension i brought upon the towing cable 49 the cable begins to pay out from the drum, adding such acceleration to the aircraft being launched as has been planned in the friction caused between braking surfaces (as later described in connection with Figures 37-40) which are stationary and those which are carried by the drum. From the time that the combined effects of land or sea taxiing and pull upon cable 49 along with the manipulation of the controls of the aircraft being launched cause the latter to be air borne the aircraft to be launched becomes the aircraft to be towed and the operation is a towing operation best seen in Figure 3.

There still remains the problem of casting off the tow connection from the aircraft being towed by means carried upon the air tug, which will be described in connection with Figures 31-36.

The pick-up or the aircraft being towed by the air tu is made as early in the movement of the former as possible in order that advantage may be taken of both the assistance and the pull of the air tug concurrently for the greatest length of time. The manipulation of the controls of the aircraft being launched is a highly important part in the combined launching effort to secure early and maximum launching effect from the speed attained.

The importance of mounting the tow line or loop of the aircraft to be launched upon said aircraft itself in assisted take-off will be evident because if the towing line or loop were mounted upon stationary poles movement of the aircraft to be launched would risk striking the poles.

It is therefore apparent that mounting the pick-up line or loop upon the aircraft to be launched is a distinct benefit even when assisted take-off is not intended; and this is particularly true when the aircraft to be launched is a water borne aircraft whose surrounding setting makes it difficult or impossible to use fixed loop supporting poles.

After contact has been made between the air tug and the aircraft tobe launched the pull of the towing aircraft urges the towed aircraft forward to an extent depending upon the friction of the brake surfaces in the winch as the towing cable pays out from the drum to a predetermined extent as hereinafter explained in connection with Figures 37-40. Progressive increase in the pay-out friction takes place until finally the aircraft towed not only becomes air borne but as quickly as may be desired. The construction, of Figure 3 relieves this situation by installing pay-out drum equipment in the aircraft to be towed, this secondary drum 82 may have much less inertia and therefore it allows tow line to bev payed out during the interval necessary to accelerate the primary drum on the tug.

There is a further possible benefit in the use of the two drums in that a longer total tow line length is available whether the drums have the same inertia or not.

In every case when one aircraft tows another it is necessary to cast off the tow line after the towing function has been performed. It is important that the separation of the tow line from the towed aircraft b as close "to the towed aircraft as possible in order that there shall be no fouling of propellers or controls on the towed aircraft, such as would of necessity occur if the towing cable be released at or near the tug.

Casting off the towing cable by an operator on the towed aircraft is, of course, common practice but in the present case does not cover all of the conditions which may arise.

Where the need of casting ofi the tow line is known to those in the towed aircraft, no difficulty arises, but when some emergency occurs by reason of which it is necessary for the air tug to cease towing, and in particular where there is danger of the drum-carried cable on the air tug unreeling completely from the surface of its drum, it is necessary that the cable and the pick-up line and leader be disconnected at the point at which the leader is attached to the towed aircraft. Part of my invention is directed to a quick, effective and reliable means and method by which one in control on the tug can disconnect the tow line at the towed aircraft.

The, structure by which I prefer to accomplish this is shown in Figures 31-36.

Figures 31 to 36 inclusive show the same general form of tow line fastener and release but with different throwing mechanism. It is togglelocked and is adapted for automatic release of the towing line at its rear end (at the tow end) to protect, for example, against casting off the tow line or cable from its drum on the tug. This form has been selected because to the best ad-v vantage it illustrates automatic release of a cable at the towed aircraft by means operable from the air tug. Other emergencies merely require edible? opening the control circuit on the tug jor enthe tow.

Figures 31 and 32 illustrate the same holding and .releaseimechanism of Figures 34 and 35 in closed (holding) and open (released) position adapted .for simple hand operation.

A holder or shell 95 is recessed from the exterior at 9.5 to receive a rope or cable terminal. This may be a mere noose or bend in the end of the cable or a fitting such as ring 53 upon the outer end of leader 68. Across the recess to engage the ring and hold it in place moves a bar, prong or catch .95 carried by catch lever 91. The catch lever 9! is conveniently pivoted to swing about a center 98. Pull upon the ring 63 will not release the hold, as disconnection requires reverse swinging of the catch lever.

I swing the catch lever by toggle mechanism comprising a link 99 pivoted to the catch lever at 100 and an arm IIII ivoted to link 99 at I82 and forming part of a rocker arm, the other arm of. which IQB is thrown to operate the toggle. Therocker arm turns about bolt I04 as a pivot.

In-Figure 31 the toggle is closed and locked in position and is held in this position by counterclockwise stress of spiral spring I upon arm I03. In Figure 32 the toggle is open.

"The means shown for throwing the operating leverin these two figures is conventional. through a rope I06 and" handle III'I, permitting hand throwing either locally or from a distance within the towed aircraft. The rope I06 in Figure .34 may be the same .rope except that it is pulled hydraulically.

In Figure 34 the catch and release are intendedto be of the same general character as in Figures '31 and 32 but the toggle levers'are controlled hydraulically by means of a pump Hi8, pressure tank IIIl, exhaust tankIBQ and a valve III connected by suitable conduits. The valve controls pressureto and from a cylinder II2 whose piston .I'IS pushes lever H4. When valve III is turned to connect the cylinder with the exhaust, piston .I I3 is' returned to its initial position (to the left in the figure) by the pull of spring H5. The piston rod is connected to the lever at IIS and one end of the spring is connected to' the lever at In and the other end .to a fixed'point at II 8. The 'lever'is fulcrumed at H9 and its short end is connected at I20 to rope I06.

W th the connections as shown the valve ILI can be turned by hand or. .by any other means to a point at which the position of the lever H4 is determined by the pull of sprin H5 so that the rope I06 is slacked and the latch remains closed oriis closed by stress'of the spring I85. The parts will therefore remain generally in the position shown in Figure 34 until operation of valve II I brings pressure to bear upon piston I I3. This pressureth'rows the lever II4 in counterclockwise direction as, seen in Figure 34 bringing tension upon the connection I06, swinging the arms Hi3 and IIJI in clockwise direction to open the latch to the position seen in Figure 32.

The latch can therefore he opened by hand either byv turning valve III or by turning lever I I- I in counterclockwise direction and canbe operated from a distance by any mechanism whichwill turn the valve II I.

in Figure 34E turning mechanism for the valve I,.I. I is slifown which is capable of distant control in the same general manner as is more clearly described in connection with Figure 35 For this res onse much only of this mechanism in Figure er egatedest eme ar i possible for-Hits operation to be thoroughly urn-- derstood by comparison with the illustration at the left in Figure 35.

In the valve III the valve plug I21 is shown as having valve passage I 22, adapted when .the valve is turned to connect conduit I23 leading to the pressure tank IIEI with conduit I2? leading to the cylinder. Valve passage I2 3 connects, as shown, conduit I25 leading to the exhaust tank I59 with conduit I27 leading to the cylinder. Passage I26 continues to be connected with the cylinder whether inlet or exhaust conduit is in line with either passage I22 or passage I24.

As will be seen in the position shown, the operating end I28 of the cylinder is connected to exhaust conduit I25. With slight clockwise movement, the operating end of the cylinder will be connected :with pressure conduit I23 thereby displacing the piston to the right, shifting the lever IIll against the tension of spring H5 and breaking the toggle.

The valve operating lever I29 is urged to the left, i. e. in clockwise direction by spring I30 anchored at IEI but is restrained from this movement by catch I552. The position of the catch and valve in Figure 34% corresponds to the closed toggle position in Figures 31 and 34. When solenoid I33 is operated by distant control-as, for example, in Figure 35+the catch is released and the latch is thrown by spring l39 in clockwise direction to allow pressure to be exerted on the piston thereby opening the toggle. A stop I3 3 prevents overtravel of the valve plug.

In Figure 35'fragmentary portions of two air-. craft are shown, one towing (air tug) t5 and the other the tow in process of being launched, indicated at M An electrically conducting cable 49 forming a section of the tow line pays out from a drum such as 8e (Figure 37) in aircraft 45'.

Both aircraft are modified so that mechanism on the towing aircraft rovides remote control of a release carried by the towed aircraft. The release shown may be and for simplicity of illustration is assumed to be substantially the same as that in Figures' l and 32 with the exception that the arm I93 of these figures becomes a latch I93 which is held in'place by a catch I35 come parable with batch I32 in Figure 34*. This catch is withdrawn to release the latch by the armature i 35 of solenoid I31.

In an emergency, such for example as that created when the towing cable has been payedout excessively and is in danger of being cast oil the drum, the solenoidis operated bye relay cite. cuit I38 using'localbattery I39. The local circuit, normally open, is closed by. a switchoperated b a radio receiver or manually by switch MI 7 The radio receiver is so turned. that it receives impulses from a radio broadcaster I40 on the towing aircraft. The broadcaster carries its own suitable source of electric current. As it is primarily for emer-w ge'nc'y use it is held inoperative by maintaining its circuit normally open. This is done in the illustration by a local circuit M2. The local circuit is intended to be controlled automatically but it, as well as'the broadcaster circuit, can be operated manually to transmit a signal either directly, through hand switch It? which closes the broadcaster circuit I 44, or indirectly, by switch I which opens the local circuit I42.

When the relay I46 is energized-as is normally the case-its armature I48 is pulled-down against the pressure of a spring L4]. 'The spring 13 engages the head or the armature'which is in the form of a switch bar I49. In the absence of current in the circuit the switch bar engages contacts I50 in broadcaster circuit I44.

My invention contemplates fully automatic control over the broadcaster to the extent that at any predetermined length of cable pay-out desired, the relay shall be de-energized to transmit a signal from the broadcaster on the tug to the towed receiver.

The broadcaster control relay is operated by an electric current from batter I5I, one terminal of which is grounded at I52 to the tow aircraft structure. The other terminal is connected to the relay I40 and from thence to pulley 90 through normally closed switch I45. The struts I54 and I54 supporting pulley may be insulated at convenient points such as I55. From the pulley the current passes to the cable 49' and then returns to ground I50 through the drum and winch support not shown.

It will be understood that the struts IM and I54 of Figure 35 may be the same as struts SI and 03 of Figure 37. The need of incorporating an insulated pulley in the guide mechanism of Figure 37 or of installing an additional pulley depends on each individual installation.

So long as current continues to pass from ba tery I5I through relay I46 and the cable to ground, the relay will continue to draw its armature down, maintaining the broadcasting circuit open; however, when the cable has been payed out to a dangerous extent, a length of insulation I51 previously set upon the cable at the desired point passes over the pulley 90, interrupting the circuit through the relay winding and causing the broadcasting circuit to be closed through its otherwise open contacts. The broadcasting impulse is then transmitted.

The radio receiver acts from this impulse, the solenoid I3! is operated and the cable is released.

In Figures 41 and 42 the structure of Figure 39 is modified to provide release of the tow line from a secondary winch on the towed aircraft by remote control from the towing aircraft.

A local circuit on the towed aircraft corresponding closely with the remote control shown in Figures 34 and 35, actuates the armature of a solenoid which is remotely controlled to remove the braking force from the secondary drum thereby allowing the leader or tow line to unwind rapidly therefrom.

In Figure 41 a spring IBI corresponds with spring lfiI of Figure 39 but instead of abutting a washer attached to rod I 66, spring I5I abuts flanged collar 205 which in turn abuts an annular helical spring key 207 held in position by retaining sleeve 208.

v The pressure of spring I6 I in normal operation is transmitted through flanged collar 205, helical spring key 207, grooved sleeve 206, to rod I60.

To provide remote controlled release of the pressure of brake spring IGI the armature of a solenoid I31 responsive to radio signals in a similar manner as illustrated in Figure 35 is connected to slidable sleeve 2I0 through cable 2H and tab 2i 2. When the solenoid circuit is closed, sleeve 210 is displaced to the left in the figure until it abuts the flange on retainer 208 and forces the retainer to the left against the pressure of spring 209. This in turn allows helical spring key 207 to expand outwardly from its seat, premitting collar 205 to slide on sleeve 206 thereby relieving pressure of spring IS! on the brake discs I59 and I60 in Figure 38 and allowing the leader to pay out.

When reference is made herein to operation'of a mechanism through a solenoid within a circuit, the reference is intended to cover any electrically operated device within such a circuit and a solenoid is referred to because of its adaptability for this use and its low cost.

It has not been necessary to devise novel broadcasting and receiving control units since many structures and methods of operation are known for distant control by broadcasting transmitters acting through receivers which respond to the transmitter impulse to close a local circuit. All that is necessary, therefore, is to provide for closing normally open contacts in the transmitter circuit on the towing aircraft thereby correspondingly closing the local circuit upon the towed aircraft by operation of the receiver mounted thereon.

It is recognized that many impulse-transmit ting mechanisms are available along with receiving mechanism which are used in connection with them.

In order that there may be no question about the full operativeness of this part of my mechanism I would state that any transmitter capable of operating a relay by means of a receiver, with any relay capable of operating a solenoid under remote control conditions will serve the purpose here.

Among a great many of those which are known and available I would refer to a few patents which disclose remote control systems of suitable character. See Hammond 1,653,172, in which the relay of the radio receiver would serve a like purpose here, so that with radio impulse a local battery Will operate through the solenoid;' Walker, 2,178,089 in which any of the combinations of the radio receiver would be effective to throw current to the solenoid; Gray 2,137,719 in which the receiving device of Figure 2 could operate the relay instead of the lamp; and Cumming 2,214,101 in which any one of the control switches proposed could be used for the present purposes.

Since the time of the broadcast and therefore the time of release of the catch in Figure 35 is dependent upon the position of the insulation upon the tow line, the release of the tow line will take place at any predetermined point and is automatic.

The motor and drum constructions of Figures 37 and 38 are effectively special winches, and, although having much in common, difier slightly. Figures 38, 39 and 40 are partly diagrammatic.

Describing the form in Figures 38, 39 and, 40: The drum 841' afiords a support for the cable 49 upon which it is wound and from which it is payed off as the stress from the launching of the aircraft requires. The resistance to pay oil at the start is relatively small but increases progressively until the aircraft launched is not only air borne but is towed at the same speed as the speed of the air tug. i

The drum and the brake support I58 are frictionally connected through annular brake discs I59 and I60 which are interleaved and are connected alternately one set to the drum and the other set to the brake support. These discs permit relative movement of the brake support and the drum subject to the friction between the discs, which friction as later pointed out in-. creases automatically when pressure of brake spring IBI is applied through brake levers I62 fulcrume'd "at I 63, keys IE4 andpressure plate IE5.

The pressure of spring 'IGI is applied gradually tothe levers IE2 through a rod $66, tube I61 and washer I68. The washer bears against the tips of the levers IE2 (see Figure 39) causing them to swing about their outer end 'fulcrums. The relative positions of the tube IG? and the rod I66 may be adjusted by means of a brake spring adjusting nut I159 which is threaded on rod 156 and bears against the tube I61. When the nut is turned the pressure of spring I6! may be increased or decreased.

The axial movement of tube 161 "which applies pressure to brake "levers IE2 is controlled through a double yoke I70 pivotally attached to a coupling III which is welded to tube I61. The yoke IIB is pivotally connected at its opposite end to a cam I12 upon a threadedshaft I13 suitably supported.

When the nut I8li is turned on the threads I14 of shaft 173 by handle II5, cam IE2 is displaced to the left in the figures. This in turn operates yoke I'IO (Figs. 39 and 40) counterclockwise and displaces tube I81 and rod P66 axially to the right thereby removing spring pressure from brake levers IE2. In this position, the winch is set for a pickup.

As soonas contact is made and the line begins to payout, gear I16 secured to the drum turns gear II'I with which it is meshed and thereby turns shaft 1 I3.

The nut I89 is prevented from turning with the'shaft I13 by means of a dog I18 and handle I15. The nut is displaced to the right in Figum 38. "Cam I12 is urged against nut Hill by spring 'IBI acting through rod I66, nut 89, collar III -and yoke 110. In the 'above manner the controlled displacing of the nut I86 on shaft I13 permits the brake spring'pressure to be applied tobra-ke discs I59 and I80.

Arm 'IGI carrying pins maybe turned so that the pins will cooperate with cam faces I82 thus permitting various initial displacements of nut I80. In this manner the number of "turns made by drum 84' from the instant the line starts to payout until the'brake is'fully applied may be regulated. A conventional level wind device indicated by I86 is also driven from gear I'IG through shaft I81 and chain and sprockets. .It has no part 'in'my invention.

The reversible electric motor I83 drives "the various mechanisms involved'including the brake discs, and brake support frompinion I through ring gear I85.

The unit shown in Figure 138 'per se, that is aside from the combinations into which it enters in .my present application, .is the .invention of Arthur B. Schultz who has filed an application for patent upon it having Serial No. 472,600, filed January 16, 1943.

Insofar as may be necessary to complete the disclosure of this application, the Schultz application is incorporated by reference.

The structures of the hook and hook. retainer 1 6 guide 181. The "track stops at the upperender the hook retainer.

The hook retainer takes over the controlof the hook, holding the guide I81, and hence the hook, in place yielding ly and permitting the hook to be withdrawn when stress from the take-off exceeds the predetermined resilient resistance of the retainer.

.The body I88 of the arm is tapered towards the end supporting the hook retainer and is, thereforepreferably made of 'WOOd to facilitate this construction and to save weight.

.The flanges I86 ofithe track I86 .are partly enclosed within the overhanging edges I81 of the guide I81.

As the hook guide 181 frees from the'track it passes within aipocket in the hook retainer. The pocket is flanked by spring :side plates I89, I90, inwardly turned atthe top to 'form lips I9I and I92. These lips engage the upper outer surfaces 581 of the hook guide and resiliently restrain the hook guide, holding the hook to the arm while the guide is passing from the track and after the guide has passed beyond the lower end of the track.

The spring side plates I89 and I98 are reinforced on the outside by spring supports I93. These extend to the end of the hook retainer, and at the rear of the plates are further supported by short straps I93 riveted'to the arm'through thespring supports and the spring side plates.

Inside the spring side plates is a supporting and stifiening channel strip I54 shown in section in Figure 29 as of inverted U-shape. The bar of the U limits the upward movement of a spring detent 95 whose upwardly turned spring seen in Figures-2'7, 29 and 30 are also the .in-

pose :a race bflthfil'mfiklis formed as a T-slo'tted end I96 forms the detent .and restrains withdrawal of the hook from the end of the hook retainer.

The spring I and its upturned end act as a tongue. During withdrawal of the hook from the hook guide the tongue is downwardly sprung by. thehookguideintoa space I91 cut away from the material of the arm. As thus constructed the hook guide can pass out to the right in Figure.27 when the stress upon it is strong enough for the purpose.

The .actualrelease occurs sometime after the contact of the .hook with the pick-up loop or line and between that time and the time when towing .stress .is' brought upon the aircraft to be towed. After the release takes place the "hook is supported wholly by the towing line 49 through clevis r98.

The'spring side plates and tongue give considerable flexibility to the hook support so that the hook can .leave the support directly at the bottom or by torsion, springing the lips to assist in the release, or by a combination of these.

The hook body I99 connects with a tapered gathering prong 280 which guides the pick-up loop or line into a recess 281 having end pockets 2G2, 233.

Elastic inserts within'the loop or line would be quite desirable but springs and rubber ropes or cablescannot be used in the pickup because though they yield very desirably their immediate recovery after stretching causes them to throw the loads picked up almost as-projectiles.

'I contemplate using a special material within the towline, preferably in the pick-up loop or line or in the leader to absorb energy without the objectionable spring-likerebound, 'etc. Materials which have this ability to absorb shock without this rebound are'found among synthetic 17 linear condensation polymers, vinyl type plastics, rubber hydrochlorides, cellulose esters and cellulose. Several of them have well known trade names such as Nylon, Vinyon, Fortisan, Saran, and Laminite.

These materials have to a greater or lesser degree, nylon to a comparatively high degree, the characteristics of good elasticity (ability to return to normal length after being stretched), long elastic memory (hysteresis or energy absorption) combined with high percentage elongation. It is desirable that such a material have at least 10% elongation under maximum working stress. However, there is no objection if the material has up to several hundred percent elongation provided it has the other characteristics. In the case of Nylon, it has been found that elongation under maximum working stress will run between 20% and 40% depending upon the composition of the particular Nylon.

The above characteristics permit the line to yield considerably under stress but to return slowly after the accelerating force is removed, thus preventing overshooting or rebound of the load.

With the use of one or some of these materials, I am able to cushion the shock of initial impact when the pick-up loop or line is stretched, thereby relieving the stress while the inertia of the drum and pay-out cable of the tub at one end and the inertia of the moving, but slowly moving, assisting tow at the other end are being overcome.

It will be understood that the shock absorbing characteristic of the materials suitable in my invention provides relatively long elastic memory as compared with rubber or a steel spring; nevertheless, there is a substantial recovery within a few seconds after the load has been removed. This permits successive pick-up or launching operations with the same tow line.

With a large and heavy aircraft to be launched, it may also help to overcome the inertia of a second (smaller) drum and pay-out cable, carried upon the aircraft to be launched.

- The length of pay-out of cable may also be reduced.

Thus I have applied the eflicient shock-absorbing properties of Nylon and similar materials to the launching of an aircraft by means of another craft in full flight. The energy absorption within the loop or line and the pay-out of cable from a drum on the tug, and in certain cases the pay-out of cable from a drum on the towed aircraft having less inertia than that of the drum and cable on the tug, all contribute to relief of the shock of the pick-up, acting substantially in series to accomplish this purpose and to the best advantage quickly and smoothly to accelerate the launching of an aircraft.

Nylon as described herein is a synthetic linear condensation polyamide which has been colddrawn so as to develop a very strong tendency to contract to its former length after it has been stretched.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

' 1. In an aircraft launching system, an aircraft intended to be launched, releasing supports for a line mounted upon the upper surface of the aircraft, and a towing line supported from said supports and extending free from interfering aircraft structure in a direction transverse of the aircraft's direction of travel.

18 2. In an aircraft launching system, an aircraft intended to be launched, a pair of posts mounted upon the upper surface of the aircraft, and a towing line supported from said posts and extending transversely of the aircraft's direction of intended travel.

3. In an aircraft launching system, an aircraft, a towing line, pole means for spreading the line and mounted upon the upper surface of the aircraft, and connections from the surface of said aircraft to the line released by pull on the line, whereby when the line is caught by a towing aircraft the spread part of the line is freed from connection with the upper surface of the aircraft.

4. In apparatus for launching one aircraft with the assistance of another aircraft, an airplane body having an upper surface, wings empennage, and power plant, a launching line releasably mounted on and attached to the airplane to form a stretch above the upper surface of the body, a towing aircraft having a depending arm, a

tow cable, and a hook fastened to the end of the leasably holding the launching line and sockets for supporting the poles permitting the poles to pass out therefrom as the launching line is disengaged from the clips.

6. On an aircraft adapted to be launched, sockets upon the upper part of the aircraft and hav ing openings from the sockets away from each other adapted to permit fall of pole from the sockets outwardly, poles mounted one within each socket, a towing loop having a towing connection with the airplane at one end and spread by the poles, and clips connected with the poles engaging the loop, the loop being adapted to be freed from the clips by pulling upon the loop and then permitting the poles to fall free of the sockets.

7. On an aircraft to be launched by means of another aircraft, a launching line, spaced poles for supporting said launching line, said poles being of loosely fitting telescopic construction whereby the poles collapse in the absence of lateral pull, and clips on said poles for releasably holding said launching line, the pull of said launching line being used to hold the poles in extended position taut whereby the poles are adapted to collapse when the pull of the launching line is removed.

8. In an aircraft launching system, an aircraft to be launched by means of another aircraft, a 0 launching line, spaced poles for supporting said launching line, said poles being of telescopic construction, hydraulic means for extending the telescoping parts of said poles, and clips on aid poles for releasably holding a launching line.

9. In an aircraft adapted to be launched, sockets upon the upper part of the aircraft, poles adapted to fit releasably within the sockets and a towing loop connected to one end of the aircraft, spread between and connected to said poles, whereby when the loop is caught by a towing aircraft the poles are pulled from their sockets by stress upon the loop and are suspended from the loop during towing of the plane.

10. In launching apparatus for aircraft, a to ing aircraft, a pick-up loop carried by the aircraft to be launched, a shock absorbing winch drum .and connections carried by the. aircraft-to be launched and comprising. supportscarried by the said aircraft to. be launched, extending. above. the-upper surfacerofsaid aircraft andaclapted. to hold the. towingloop of said aircraft tube.

launchedin transverse positionto be :pickedup by the towing hook;

11. Inalaunching system for aircraft, an air.-

craft adapted in flight to pick up the aircraft. to.

belaunched, a. metallic towing cable thereon, a

drum on whichthe cableismounted, a. switch, a

broadcaster. upon said-aircraft having. a. circuit adaptedto be closedrby the.switch, a..relay circuit maintaining said switch in. open. position whenrthe current is on said circuit, abattery. and. connections: for said relaycircuit passing current'through said relay and through a..portion. of-said cable length andinsulation meanszcarried by said cable. for interrupting, the circuit through the relay when a predeterminedlengthof cable has-been'payed out thereby causing said broadcaster to transmit an impulse.

12. In. a system for automatic control of .a. cir-- cuit-upon a towed aircraft,a towedaircrafta. towing aircraft,,a transmitting circuit on.- said towing aircraft adapted to broadcast whencurrent passesthrough said circuit, a. receiving circuit on said towed aircraft, a localrelay circuit on saidtowed aircraft operated-inresponse'to impulses; frmthe. towing aircraft, and electromagnetic meansactuated whena predetermined amount of towing-cable has been payed out, the

means so constructed. and arranged that th radio.

whereby; the transmitting; circuitjs permitted to.

close.

14. A towing aircraft, a tow line, arbroadcaster, a'towed aircraft, a radio receiver thereon, a fastening-forthe :line thereon, a leverby which the fasteningis closed, a. spring tending to .openthe lever, a radio receiver solenoidaloperating means for release-of the fastening, controlled by;the-re-. ceiver; the. broadcaster and: towing linebeing. mounted 11130112 61163 towing aircraft andtheother elements. mounted: upon the towed aircraft.

In. mechanism. for. launching an aircraft, anaircraftto-be launched,: acmain shock absorbingewinchincluding; a drum, towcable, brake .fon

thepdrum. and means for reelingin cable. which has: been. payed outfrom the drum, all located on the: aircraft tobe launched, and. a launching aircraft having afrelatively smallwinch for accelerating the drum ofithe main winch includin a: drum, towing cable, brake for the. drum and meansfor. reeling, in the.- Cable-whichhas. been.

20- payedout from'the drum, whereby cable maybe payed out from-both drums, the drums may be.- brakedandthe cable may bereeled. in on both drums.

16. The method of assisting the take-elf of a first aircraft by a second aircraft, which consists in. supporting atowing line in a transverse posi tionupon. the first aircraft, in picking up the line by a towing aircraft in flight, in pulling the tow line free from its support and at the same time releasing the support from the first aircraft and in continuing to tow the towed aircraft while manipulating the controls of the towed aircraft so as .to cause it tobe air borne.

17. In. the method-of launching aircraft, the steps which consist in supporting andstretching a take-off line. upon and above said aircraft in positionto be pickedup, in picking upthe'takeoff line by an aircraft in flight, in manipulating the controls of. the aircraft. to be. launched so as to cause it to beair. borne and in disengaging; the take-off line at theaircraft. to-betowed-by control effected from the aircraft-in flight.

18. In the method. of launching; aircraft, the steps which consist in supporting and stretching a take-off lin upon and above said aircraft in position to bepicked'up, and concurrently using the stretching. of the line to hold. the support in position upon the: said aircraft to be launched,- in picking up the taker-off'line'byan aircraft in flight, and concurrently releasingthe line support and in manipulating the controls of the aircraft to be launched so as to cause it to be. air borne.

19. The method ofassisting the take-off of a first aircraft by asecond aircraft, which consists in supporting a towing; line in a transverse position. from thefirst aircraft; in picking up theline by a towing, aircraft in. flight, in. pulling the tow line freefromits suppcrtand at the same time pulling the supports freefromthe craft towed, in carrying the supports along with the tow'line and in manipulating. the. controls of the aircraft to be launchediso. as to cause it to. be air borne.

20. The method of assisting a first powered aircraft by a second. aircraft in'fiight; both aircraft having drum wound tow lines and? means for allowing-the-towlines to pay out, fonbraking the. drums, which consists in picking up'the'tow line of the first aircraftto be launched by the tow line-of the second aircraftin'flight; in paying out bothtow lines, and in concurrently retarding'thetow lines whileusing the DOWGIzOf the first aircraft and its controls. to assist in bringingit into the airat speed.

21. In the method of. towing aifirst' aircraft by a second aircraft in flight, the steps which consistin picking up a towing loop from the first aircraft by a towing. aircraft in flight, in continuing the flight of thesecond aircraft to tow theflrstaircraftand in-releasing the tow rope from thefirst aircraft atiits.towedendbyenergy supplied. from. the towing aircraft.

22..I'he. method of. controlling; an automatic broadcaster transmitting impulses from a towing, aircraft having ametal towingcable wound (upon a. drum. which consists in electromagnetically. rendering the broadcasting circuit inoperative by electric current passing through a circuit ineluding a stretch off'the. metal. towing cable and opening this circuit through the cable by insulation carried by. the cable and at a time determined by the position. of. the insulationonthelength.of. the cable.

23. In an aircraft launching. and..towing.sys.-

tem, a first aircraft acting as a tug, a radio broadcaster carried thereby, means for operating said broadcaster to give a broadcast therefrom, a radio receiver carried by a second aircraft to be launched and towed, a towing connection between the aircraft, a movable holding device by which the connection is secured to the aircraft to be towed, hydraulic means for shifting said holding device to cast off the connection at the aircraft to be towed, a valve operating the hydraulic means, spring means tending to operate the valve and electromagnetic means connected with the valve and energized by an impulse within the receiver whereby a transmitted impulse from the first aircraft actuates the solenoid and permits the spring to operate the valve.

24. In a mechanism for launching and towing an aircraft, a first aircraft comprising a tug, a second aircraft adapted to be launched and towed, drums and cables thereon, one drum and cable on each aircraft, a pick-up and towing line connecting the outer ends of the two cables, brakes adapted progressively to be applied to the two cable drums to permit limited pay-out from the drums and then to stop pay-out, and remote control means including a transmitter on the first aircraft and a radio receiving instrument and local circuit on the second aircraft for releasing the brake upon the drum of the second aircraft, whereby the said drum of the second aircraft is free to pay out all of the cable upon said drum and wholly disconnect the second aircraft.

25. In a system for disconnecting a towing aircraft and an aircraft to be launched and subsequently towed, including a tug aircraft having a drum-wound cable, and an aircraft to be launched and a pick-up line connected therewith, in which the pick-up line is connected with the second aircraft to be launched by a movable bar, and the towed aircraft has a local disconnecting circuit, the method which consists in hydraulically controlling the position of the bar to connect or disconnect the pick-up line in operating the hydraulic mechanism by a valve, in spring-predisposing the valve toward disconnecting valve position, in holding the valve in position such that the tow line continues to be connected with the second aircraft, in electromagnetically releasing the valve to permit spring disconnecting operation of the valve and in passing current through the local circuit upon the second aircraft by an impulse transmitted from the first aircraft and received upon the second aircraft.

26. In a launching and towing system for aircraft, a first aircraft comprising a tug in fiight 22 and a second aircraft intended to be launched and subsequently towed, each having a drum, a cable wound upon the drum, and a brake restricting the length of pay-off of cable from the drum, and the second aircraft having a pick-up line connected with the outer end of its cable, the method of launching, towing and subsequently disconnecting the second aircraft which consists in connecting the pick-up line of the second aircraft to the outer end of the cable of the first aircraft, manipulating the controls of the second aircraft while paying out cable from both aircraft restrictedly to launch the first aircraft and subsequently disconnecting the tow aircraft at its drum by remote control from the first aircraft by broadcasting an impulse from the first aircraft, picking up the impulse by radio reception upon the second aircraft, and in relaying the impulse picked up and using it electromagnetically, to release the drum brakes of the second aircraft and permit its cable to pay out Wholly from the drum of the second aircraft.

RICHARD C. DU PONT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 986,644 Rentschler Mar. 14, 1911 834,658 Chanute Oct. 30, 1906 1,792,937 Sperry Feb. 17, 1931 2,124,867 Akerman July 26, 1938 2,252,554 Corothers Aug. 12, 1941 1,459,884 Goodin June 26, 1923 1,908,408 Cox May 9, 1933 2,102,604 Arndt Dec. 21, 1937 1,458,710 Kolczewski June 12, 1923 1,735,385 Fisher Nov. 12, 1929 2,014,557 Clampitt Sept. 17, 1935 2,131,610 Arndt Sept. 27, 1938 2,250,153 Cooper July 22, 1941 FOREIGN PATENTS Number Country Date 292,826 British June 28, 1928 506,680 British June 2, 1939 103,585 Swiss Feb. 16, 1924 QTHER REFERENCES Publication Aeroplane, Nov. 15, 1940, pages 

